Fertilizer processes and compositions using s-triazines

ABSTRACT

Process of furnishing slow release nitrogen to field soil comprising inserting and distributing in the soil in particulate or granular form melamine, ammeline, ammelide, cyanuric acid, mixtures thereof, their salts, and mixtures thereof.

This is a division, of application Ser. No. 305,394, filed Sept. 25,1981, now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to a new fertilizer process. The fertilizermaterial used in the process is characterized by poor solubility in pH 7water at ambient temperatures in the soil and by slow conversion in thesoil to a form in which it is useful to plant life growing in the soil.

There is a continuing search and need for improved fertilizer materials.For example, while ammonium nitrate, containing 34% N, still rankssecond only to ammonia, 86% N, as a source of fertilizer nitrogen, itsuse generally has been decreasing, in terms of market percentage, since1965. The reason is the increased use of the higher nitrogen contentmaterials, ammonia, with 82% N, and urea, with 46% N, respectively. Theuse of urea is a development of recent years, and may have been promptedin part by a desire to reduce shipping costs.

All of these nitrogen fertilizer materials just mentioned are readilysoluble in water. They are therefore subject to leaching, and their useresults in a rapid release of their nitrogen. Since this necessitatesrepeated applications for sustained growth, or one application withhigher leaching losses, there have been many developments relating toslow release nitrogen fertilizer materials. Generally such materialssacrifice nitrogen content for some degree of control over nitrogenavailability.

Melamine and its hydrolysis products, ammeline, ammelide, and cyanuricacid, have often been considered as potential sources of nitrogen forincorporation in fertilizer compositions or for utilization as nitrogensources per se. Melamine has a nitrogen content of 66.6%, so that abouttwo thirds of its weight is nitrogen. If it could be used as afertilizer material, it would obviously provide a good deal of nitrogenper unit weight applied. However, at present it is more expensive thanurea. Moreover, commercially produced melamine is available only as afine crystalline powder. It is manufactured in the form of very finecrystals because small size particles are required for the presentcommercial end markets for melamine, such as, for example, theproduction of melamine-formaldehyde resins and the production of fireretardant paints.

A typical screen analysis for one commercially available melamine,conducted with United States Standard Sieve screens, is as follows:

    ______________________________________                                                        Percent                                                       Screen Analysis Retained                                                      ______________________________________                                        40 Mesh           0-0.1                                                       40-50 Mesh        0-0.1                                                       50-60 Mesh        0-0.3                                                       60-80 Mesh      0.5-5.0                                                       80-100 Mesh     1.0-5.0                                                       100-200 Mesh    13-30                                                         200-325 Mesh    13-30                                                         Thru 325 Mesh   40-60                                                         ______________________________________                                    

The commercially-produced small melamine crystals are desired by theresin producers because the small crystals dissolve more readily, andany larger particles, if present, would tend to require a longerprocessing time; therefore, the larger particles are less desirable. Inthe fire retardant paint market, the melamine crystals are dispersed inthe paint, where the current fine particle sizes produce a smoothertexture in the dried paint than would larger particles.

The fine particle sizes of the commercially available melamine productsmake melamine a product that is not very attractive for agriculturalapplications. The fine particles, if applied to the surface of theground, would be blown away by even mild winds. If applied by air, asfrom an airplane or helicopter, drifting would be a serious problem andwould cause uneven application. If applied through mechanicalapplicators, the fine particles would tend to form bridges and thuswould plug transfer and dispensing lines. These difficulties in handlingthe commercially available melamine solids would make any large scaleagricultural application impractical. Nevertheless, there have been manyinvestigations into the possible use of melamine as a fertilizernitrogen source, generally on a small scale where the limitationsimposed by the fine particle size of melamine were not a seriousobstacle. However, in most cases, negative recommendations weregenerated, for reasons having little or nothing to do with melamine'sfine particle size.

In 1937, as reported in Industrial and Engineering Chemistry 29,202-205, Scholl and three associates working within the U.S. Departmentof Agriculture evaluated melamine sulfate, melamine phosphate andmelamine nitrate in connection with the growth in pots of fine loamysand of wheat and millet. These salts were compared with other nitrogensources, including cyanuric acid, urea, and, used in combination, sodiumnitrate and ammonium sulfate. The sulfate and phosphate salts ofmelamine were reported to be substantially less soluble than melamineitself, whereas melamine nitrate was said to be slightly more solublethan melamine at 29° C. Melamine nitrate was considered to producefavorable results, but the results from the other two melamine saltswere not so good. In pot growing tests with German millet and withHungarian millet, the melamine nitrate salt gave the best results of thethree melamine salts tested, and produced yields practically equivalentto those produced with control tests using urea and calcium cyanamide,but produced growth below those obtained with sodium nitrate. Finally, aseries of nitrification tests were carried out with all three salts. Theresults obtained indicated that only about 1 % of the nitrogen contentof the melamine was converted to nitrate in Norfolk loamy fine sandduring a period of 13 weeks. This is in contrast to a conversion of 80%observed with ammonium sulfate. All in all, the results obtained seem tohave been discouraging, particularly as to possible fertilizer use ofmelamine per se.

In 1941, some evaluations of melamine and melamine salts were carriedout at Kyoto Imperial University, as reported in a Japanese publication,15 J. Sci. Soil Manure, 559 (1941), in an article entitled, "Studies onthe Fertilizing Value of Melamines and Guanidines". In a ten weekexperiment in paddy soil, it was found that melamine ammonified veryslowly because biochemical degradation of melamine proceeds at a veryslow rate in the soil. The conclusions of the authors were essentiallynegative with respect to the fertilizer use of melamine and its salts inconnection with rice and barley. The authors concluded these crops didnot respond in a positive way.

West German Pat. No. 926,853, in 1954, suggested the use ofmelamine-formaldehyde resins as binding agents for granular fertilizercompositions also containing spent sulfite liquor and superphosphate. Iffield trials were made, they are not reported in the patent.

Very little nitrification of melamine was observed in a study by Clarket al. in 1957, as reported in Abstracts, 132nd Meeting, AmericanChemical Society, New York. Clark et al. reported that potassium andsodium cyanurates nitrified slowly for 6 weeks, followed by a more rapidand complete release of organic nitrogen between 6 and 9 weeks. Ammelineand mixtures of ammelide and ammeline nitrified at maximum rates betweenthe 9- and 12-week incubation periods. Very little nitrification ofmelamine was observed over a 15-week period of incubation in soil media.

In 1961, T. G. Zarger published an article entitled, "Comparison ofSlowly and Rapidly Available Nitrogen Fertilizers for Nursery Productionof Pine Seedlings", in Tree Planters' Notes No. 66, pages 8-10. Zargerstated that there had been some interest in slow-dissolving fertilizerforms that might make nitrogen available over a longer period of time,as compared to the standard nitrogen sources that had been used in thenursery for the previous several decades. The author reported acomparison between ammonium nitrate, ammonium sulfate, sodium nitrate,urea, and diammonium phosphate, as standard, readily soluble nitrogensources, with melamine, oxamide, ureaform, and magnesium ammoniumphosphate, as slowly soluble or practically insoluble nitrogen sources.All of these fertilizers were applied to nursery beds prior to seeding,at a uniform rate of 100 pounds of nitrogen per acre. The tests wereconducted with both loblolly pine and shortleaf pine. The resultsobtained seemed to indicate that all other nitrogen sources arepreferable by far to melamine for the production of loblolly pineseedlings, with somewhat similar results for the production of shortleafpine seedlings. For average height growth and survival, melamineperformed poorly with respect to both loblolly pine and shortleaf pine.The results were not as good as those obtained over a two year periodwith ammonium nitrate. The author apparently doubted that any nitrogenwas available to the seedlings from either melamine or oxamide, andconcluded that the nursery tests did not show any of the poorly solublenitrogen sources to be any better than standard ammonium nitrate.

In 1964, Hauck and Stephenson published an article in Agricultural andFood Chemistry 12, 147-151, describing the rate at which symmetricaltriazines converted in the soil to a form useful to plants. Forevaluation, melamine phosphate and melamine nitrate were recrystallized,respectively, washed, and dried. What the authors refer to as granulesof melamine, acid, and metal ion were prepared by forming dried pastesof the several materials, then crushing and screening. Such materialsincluded mixtures, for example, of melamine and phosphoric acid,melamine and nitric acid, and melamine and ferric ammonium sulfate. Inaddition, the performances of melamine, ammeline, ammelide, and cyanuricacid were evaluated in silty clay loam, in particle form, and melamineand cyanuric acid were evaluated in solution. Although some degradationof all was observed the authors pointed out that melamine and cyanuricacid degraded at a faster rate than either particles having sizes in therange from -8+12 mesh, or solutions. The authors concluded with whatappears to be a very negative observation, that the evaluation of thesematerials as slow-release nitrogen sources should be made only on cropsthat are expected to respond to small amounts of nitrogen added atfrequent intervals. In addition, the authors reported that cyanuric acidis temporarily toxic to seedlings.

Also in 1964, Terman and several co-authors reported in Agricultural andFood Chemistry 12, 151-154 (1964) that they had evaluated urea andreagent grades of melamine, ammeline, ammelide, and cyanuric acid, forcrops of corn forage and for crops of Coastal Bermuda grass, grown ingreenhouse cultures. They confirmed that cyanuric acid was toxicinitially. They found that urea and its pyrolyzate products weregenerally superior as to corn response, grass response, and also whenevaluated in field experiments with wheat. The results can best bedescribed as mixed with respect to the symmetrical triazines. Cyanuricacid was apparently considered a possible candidate for use if appliedtwo weeks or more in advance of planting, to avoid the toxicity problem.Ammelide and ammeline, and urea pyrolysis products as well, wereconsidered to be equal or superior to fertilizer-grade urea-formaldehyderesins as sources of nitrogen for Bermuda grass. They were alsoconsidered as possible nitrogen sources for use for tree and shrubfertilization. The findings with respect to melamine itself weregenerally negative. In the corn experiments, the authors measurednitrogen uptake and total dry weight, concluding that melamine did notsupply an appreciable amount of nitrogen to the crop regardless of theamount of melamine applied. Measurements taken on the dry weight ofBermuda grass clippings indicated to the authors that no appreciableamount of nitrogen was supplied to the grass by melamine. In the fieldtest with wheat, the authors measured the pounds per acre of dry forage,and found that small, insignificant increases in yields were obtainedfrom melamine, the mean yields being only slightly higher than yieldswhere no nitrogen source was applied at all. The authors concluded thatmelamine was only about 10% as effective as urea.

More recently, East German Pat. No. 120,645 described the use of apolymer coating on prilled urea to provide a slow-acting fertilizer.Prills having an average particle diameter of 1.7 mm. were pretreatedwith a coating substance or solution, dried, fluidized, and then coatedwith a latex polymer at 60° C. Melamine was mentioned as one of thepossible pretreating substances. The coated pellets had particle sizesin the range from 0.5-5 mm, preferably, 1-3 mm.

Even more recently, a publication in the Russian language reportsresults from an evaluation of melamine as a fertilizer in connectionwith one variety of spring barley: Markin et al., Tr. Slavrop S-kh Inst.40(3), 65-67 (1977; CA 21454b (1979). As understood, the Russianinvestigators compared the degradation of melamine with other standardmaterials, including ammonium nitrate, in black earth (carbonatechernozem) from the Caucasus foothills. In addition, greenhouse testswere carried out in containers of the same soil. As might be expectedfrom prior work, melamine at no point produced a nitrate level as highas that produced by ammonium nitrate.

The results reported are difficult to interpret. The control(background) apparently was fertilized with superphosphate. It is notclear whether the comparison trials using ammonium nitrate and melaminerespectively had superphosphate in the soil or not. The compostingexperiment was run without the addition of fertilizer to the soil forthe control. The spring barley greenhouse experiments apparently wererun with the addition of superphosphate for the control experiment. Inany case, the harvest, in the version with ammonium nitrate added, wasat the same level as the control (background), according to the text.The trials with melamine were considered to produce "significantlyhigher" results both as to total harvest and as to grain harvest thanwith ammonium nitrate. Further, the author reports that melamine had afavorable long term effect, in that when all of the containers wereplanted again with spring barley, and observations of growth anddevelopment were continued up to the point where head formationoccurred, there reportedly was an increase in the yield of barley, dryweight basis, as compared to the use of containers of the backgroundtype and of the type having background together with ammonium nitrate.

Because of the lack of details about experimental techniques and becauseof the very few trial runs made during the work that is reported, it isdifficult to evaluate what was done by the Russian investigators and theconclusions that they reached.

U.S. Pat. No. 3,705,019, describes the production of granular cyanuricacid from fine cyanuric acid powder particles, to produce fastdissolving granules for treating the water in swimming pools. It hasnothing to do with fertilizer.

Subsequently, Corte et al. in U.S. Pat. No. 4,083,712, producednitrogenous fertilizers in the form of salts of a cation exchange resin.In Example 3 of the patent, a sulfonated polystyrene cross-linked withdivinyl benzene, in the hydrogen form and strongly acidic, was reactedwith an aqueous suspension of melamine. The reaction product was said toconsist of 1000 ml. of a nitrogenous fertilizer containing 2.2 moles ofmelamine per liter. This material, and other ion exchange resin saltsproduced from guanidine and other nitrogen compounds, were tested over atwo year period with grass in pots of loamy sandy soil which hadreceived a basic dressing of phosphorus and potash. The first year grassyield is reported in the patent, although it is not clear what basis wasused for determining the yield. All of the salts used produced resultsthat seemed to be superior to those produced with control materials,after both one year and two year tests. In addition, based on the datareported, the melamine salt appears to have produced a superior yield toother salts, and to the control, after two years.

In what appears to be a subsequent development, described in SouthAfrican Pat. No. 735,583, Corte and his associates pursued theirinvestigations further. More work is described with nitrogenousfertilizer salt compositions comprising a cation exchange resin having anitrogen base such as melamine chemically bound thereto. The cationexchanger optionally may be partially charged with a material such asmelamine, and partially with inorganic nutrient ions. In Example E ofthis patent, a three year old lawn was used for testing differentsources of long term fertilizer nitrogen. In one group of tests, thenitrogen was entirely furnished by a "conventional long-term"fertilizer, crotonylidenediurea (CDU). CDU is a condensation product ofcrotonaldehyde and urea. It is difficulty soluble in water. In a second,comparative test, the fertilizer was a mixture of 80% by weight of thislong-term fertilizer material with 20% of a melamine ion exchange saltfertilizer. In a third test, the fertilizer nitrogen was supplied by amixture of 60% of the long-term fertilizer material,crotonylidenediurea, with 40% of the melamine ion exchange saltfertilizer. The sum of the weights from five cuttings of this grass ingrams per square meter was, for each of these three tests respectively:1654; 1757; and 1899. Corte et al. observed that after 3 months, theconventional long term fertilizers evaluated were used up, whereas withthe ion exchange salts, "no signs of exhaustion" were detectable afterfive months.

Both of these patents of Corte et al. point out that certain slowrelease nitrogen sources, such as urea-formaldehyde resins, have beencombined with a short term nitrogen fertilizer material, such as anitrate, to provide a greater initial fertilizing effect. Corte et al.observed, however, that melamine, unless chemically reacted to becomethe salt of an ion exchange resin, was "unsuitable for fertilizingpurpose", U.S. Pat. No. 4,083,712, col. 2, lines 58-61.

The Allan Belgian patent, No. 885,166, published Sept. 30, 1980,describes one way to improve the commercially available crystallinemelamine for fertilizer use. The commercial product apparently containsone or more unidentified phytotoxic impurities. The impurities areremoved by washing with room temperature water, at least once. Themelamine, being very poorly soluble in water, remains in crystallineform, whereas the toxicant is more soluble and is carried off in thewash water. Tests reported in the Belgian patent demonstrate that thewashed melamine has reduced toxicity as compared to its unwashedcommercially available counterpart.

Because of the generally negative or equivocal results reported, basedon the limited amount of work done to date with melamine, its relatedtriazines, and their salts, little or no work has been done that hasbeen concerned with the modes of application or physical forms of thesematerials. On the contrary, the work done has been addressed to thequestion of whether these triazine compounds and their salts are in factuseful sources of nitrogen, and in general, the most frequent conclusionreached was that they were not. Consequently, apparently no one to datehas investigated techniques of application, to see if any differences inresult could be observed. Perhaps such work has been inhibited by theknowledge that many substituted s-triazines are sufficiently toxic toplant life that several are used commercially as herbicides (see theGysin et al. patents, for example, U.S. Pat. Nos. 2,909,420, 2,920,421,2,923,614 and 2,936,227), and by the several reports as to the toxicityof the s-triazines themselves, as in the Allan Belgian Pat. No. 885,166,discussed above.

SUMMARY OF THE INVENTION

This invention, in one embodiment thereof, relates to a process forfurnishing a slow release source of fertilizer nitrogen to field soil.This process involves inserting into and distributing within the soil,in the root zone, often at a depth of from about 75 millimeters (about 3inches) to about 360 millimeters (about 14 inches) a granular fertilizeras described above. The granular fertilizer may be spread over thesurface of the bed, and then mechanically worked into the soil as byturning over the soil by plowing or discing.

In this process, the total rate of application is preferably such as toinsert enough total long term fertilizer nitrogen for an entire growingseason. A primary advantage of this process is that the rate ofapplication of the fertilizer generally is less than one-half of thatneeded to achieve comparable results when ammonium sulfate is employedas the sole source of nitrogen and is applied as a solution through anirrigation sprinkler system.

The process of the invention is useful for increasing the productiveunits from a crop that responds to fertilizer nitrogen. This processcomprises furnishing at least 50%, and preferably about 90%, of thatnitrogen in the form of a particulate fertilizer nitrogen sourceselected from the group of materials consisting of melamine, ammeline,ammelide, cyanuric acid, mixtures thereof, their inorganic salts, theirorganic salts and mixtures thereof.

In one preferred embodiment of this invention, the process involvesdistributing a slurry of fine melamine crystals in water as a broad,ribbon-like layer beneath the soil.

In another preferred embodiment of the invention, fine melamineparticles, or granules of the fine particles held together with abinder, are distributed over the surface of the soil, then turned underto distribute them through the root zone.

In each of these preferred embodiments, the fine particles of the poorlysoluble nitrogen source are distributed throughout the soil, in the rootzone, subject to the action of water and of microorganisms. It has beenfound that this leads to excellent results, i.e., the elimination of theneed for repeated nitrogen feedings, an increase in productive units,and possible economies.

Another preferred technique for practicing the invention is to apply thefertilizer material to the soil surface, wet it thoroughly as with waterfrom an irrigation sprinkler, then turn it under to distribute itthroughout the root zone.

Depending upon the application and distribution techniques employed, thefertilizer material may be in the form of granules. Such granules can befabricated to have strength, sizes, and weights that are suitable fordispensing mechanically for application to and into the soil. Thepreferred size range for such granules is from about 1 millimeter toabout 10 millimeters, and the most preferred size range is from 3 mm. to5 mm.

These fertilizer granules comprise a poorly soluble nitrogen source fromthe group named above, and a binder. The nitrogen source ischaracterized by fine particle sizes not above about 10 mesh, by poorsolubility in pH 7 water at 20° C., and by slow conversion in the soilto a form in which it is useful to plant life growing in the soil. Thebinder is present in an amount at least sufficient to bind together thefine crystals or powder particles of the nitrogen source, to formgranules having the desired strength. It may be a readily solublematerial that, after distribution of the granules in the soil, releasesthe nitrogen source particles to permit the action of water andmicroorganisms on the particles. The binder is selected to be compatiblewith the soil, and any residue of the binder should be either inert,biodegradable, soil conditioning or have plant nutrient value.

Granular agglomerates for use as a source of fertilizer nitrogen, fromfine particles of a nitrogen source selected from the group of materialsdescribed above, may be made by applying a small but effective amount ofa binder, to bind fine particles of the nitrogen source together. Thebinder is then hardened or permitted to harden and the agglomerates arescreened to produce product agglomerates having sizes in the range of 1millimeter to 10 millimeters, preferably. Over-sized particles can becrushed to size, and fines can be recycled.

The binder may also be a relatively insoluble material such as a ligninsulfonate, a synthetic or natural polymer applied in the form of asolution or an emulsion, or it may be a solidified soluble materialhaving plant nutritive value such as, for example, urea, ammoniumnitrate, or a combination of such materials. Suitable granularfertilizer products may also be made from fine particles of a nitrogensource selected from the group of materials described above, togetherwith a binder that is hardened from the molten state and that enrobesthe particles. Such granular products are referred to hereafter asprills.

The fertilizer process of the invention is useful for increasing theproductive units from a crop that responds to fertilizer nitrogen. Thisrequires furnishing at least 50%, and preferably about 90%, of thatnitrogen in the form of a particulate fertilizer nitrogen sourceselected from the group of materials described above, in combinationwith a soluble or fast-release standard nitrogen fertilizer materialsuch as urea or ammonium nitrate. The granular form of fertilizerproduct permits the application of both the slow release and fastrelease sources of nitrogen in a single application of granules. Theterm "productive units" is used to refer to the desired crop product.

The process of this invention is useful for such diverse crops as foodgrain, feed grain, legumes, fiber crops, vegetable oil and nut oilyielding crops, root crops, tuber crops, tree fruits including citrusfruits, tree nuts, vine fruits, bush fruits, commercial vegetable crops,commercial melon crops, and flowers. Particularly interesting resultshave been obtained in practising this process in connection with wheat,corn, rice, and potato crops.

DEFINITIONS

The term "granular" is employed herein to refer to both agglomerates andprills. Agglomerates are formed by mechanically bonding fine particlestogether using a binder. Generally the binder is applied as an aqueoussolution, and dried to cause binding. Screening and recycling are usedto achieve desired sizes. Prills are formed by mixing fine particles ina molten binder material, then chilling drops of the mixture.

The term "poorly water soluble" refers to materials that dissolve inwater at 20° C., pH 7, to the extent of 5 grams per 100 grams, or less;that is, materials that form solutions of 5% or less concentration.

The term "slightly water soluble" refers to materials that dissolve inwater at 20° C., pH 7, to the extent of 1 gram per 100 grams or less;that is, materials that form solutions of 1% or less concentration.

The term "readily water soluble" refers to materials that dissolve inwater at 20° C., pH 7, to the extent of 20 grams per 100 grams or more,that is, materials that form solutions of 20% or greater concentration.

Based on available information, the solubilities in water at 20° C., pH7, for several materials useful in connection with this invention, ingrams per 100 grams are:

                  TABLE I                                                         ______________________________________                                        Solubility Data                                                               Material             g/100 g                                                  ______________________________________                                        melamine             0.50                                                     ammeline             0.008                                                    ammelide             less than 0.008                                          cyanuric acid        0.27                                                     melamine nitrate     0.85                                                     ammonium nitrate     192                                                      ammonium sulfate     75.4                                                     diammonium phosphate 131 (at 15°)                                      potassium acid sulfate                                                                             51.4                                                     potassium sulfate    11.1                                                     urea                 119.3 (at 25° C.)                                 ______________________________________                                    

The term "fugitive" is used to refer to a vehicle that goes into thesoil. The aqueous vehicle of a melamine slurry, for example, simplysoaks into the soil, leaving the melamine particles behind. Such avehicle may contain plant nutrients, such as urea or ammonium nitrate,and may contain suspending agents.

DETAILED DESCRIPTION OF THE INVENTION

This application discloses and claims subject matter that is closelyrelated to subject matter disclosed and claimed in the companion patentapplication of G. Graham Allan, Donald E. Freepons and George M. Crews,Ser. No. 305603, filed Sept. 25, 1981, that is being filed substantiallycontemporaneously herewith. The Allan, Freepons and Crews applicationdiscloses that the s-triazine particles and/or those of their salts aremost conveniently handled and dispensed when in granular form havingsufficient strength, size, and weight for use in modern mechanicaldispensing equipment. That application describes fertilizer products ingranular form, with sizes in the range from about 1 mm. to 10 mm.,preferably 3 mm. to 5 mm, and processes for making them. They are madeup to have good drillability, a desirable apparent specific gravity, andto be substantially free from dusting. The disclosure of thatapplication is incorporated herein by reference.

This invention, in one embodiment thereof, relates to a process forfurnishing a slow release source of fertilizer nitrogen to field soil.This process involves inserting into and distributing, in as uniform afashion as is practicable, within the soil, in the root zone, often at adepth of from about 75 millimeters (about 3 inches) to about 360millimeters (about 14 inches) a particulate fertilizer as describedabove. The particulate fertilizer may be spread over the surface of thesoil, and then mechanically worked into the soil as by turning over thesoil by plowing, discing, rototilling or the like.

In this process, the total rate of application is preferably such as toinsert enough total long term fertilizer nitrogen for an entire growingseason. A primary advantage of this process is that the rate ofapplication of the fertilizer generally is less than one-half of thatneeded to achieve comparable results when ammonium sulfate is employedas the sole source of nitrogen and is applied as a solution through anirrigation sprinkler system.

In each of the embodiments of the invention, fine particles of a poorlysoluble nitrogen source are distributed throughout the soil, in the rootzone, to be subject to the action of water and of microorganisms. It hasbeen found that this technique leads to excellent results, i.e., theelimination of the need for repeated nitrogen feedings, an increase inproductive units, and possible economies.

The "root zone" for some crops is from 6" to 14" below the surface, adepth of distribution, conveniently achieved by surface broadcasting,then plowing. For some plants, the root zone begins at about 3" belowthe surface. Distribution is then conveniently achieved by broadcastingon the surface, then preferably soaking the soil as with irrigationwater, then discing under. For shallow-rooted plants or seedlings, theroot zone is closely adjacent the surface, and in this case,broadcasting and soaking, followed by rototilling, represents apreferred mode of application.

Generally the preferred technique for practising the process of theinvention is to apply the fertilizer material to the soil surface beforeplanting, wet it thoroughly as with water from an irrigation sprinkler,then turn it under to distribute it throughout the appropriate rootzone. The fertilizer material is a particulate fertilizer nitrogensource selected from the group of materials consisting of melamine,ammeline, ammelide, cyanuric acid, mixtures thereof, their inorganicsalts, their organic salts and mixtures thereof.

In one preferred embodiment of this invention, the process involvesdistributing a slurry of fine, discrete melamine crystals in water as abroad, ribbon-like layer beneath the soil, in which the individualcrystals preferably are separate, or spaced apart from each other, andnot agglomerated.

In another preferred embodiment of the invention, fine melamineparticles, or granules of the fine particles held together with abinder, are distributed over the surface of the soil, then turned underto distribute them through the root zone.

When the fertilizer material is in the form of granules, such granulescan be fabricated to have strength, sizes, and weights that are suitablefor dispensing mechanically for application to and into the soil. Thepreferred size range for such granules is from about 1 millimeter toabout 10 millimeters, and the most preferred size range is from 3 mm. to5 mm.

These fertilizer granules comprise a poorly soluble nitrogen source fromthe group named above, and a binder. The nitrogen source ischaracterized by fine particle sizes not above about 10 mesh, andgenerally, by particle sizes essentially less than about 40 mesh. In thecase of melamine, the screen analysis reported above indicates that forone commercial melamine, a majority of the particles are less than 200mesh, which is very fine. Such fine particles are difficult to handleexcept in a continuously agitated aqueous slurry, or as a suspension inan aqueous vehicle. For this reason, granular forms are often moreconvenient to use in the process of the invention, i.e., they can bemechanically dispensed and applied with greater convenience andefficiency.

Granular fertilizer products useful in the process of the invention maybe in the form of agglomerates or prills. The agglomerates may be madeby any conventional technique for agglomerating fertilizer products,utilizing the poorly or slightly soluble fertilizer nitrogen sources ofthe present invention. Thus, the poorly or slightly soluble nitrogensource in an agglomerate is selected from the group consisting ofmelamine, ammeline, ammelide, cyanuric acid, mixtures thereof, theirinorganic salts, their organic salts, and mixtures thereof. These saltsare preferably selected from the group consisting of the hydrochloride,hydroiodide, metaphosphate, nitrate, orthophosphate, orthophosphatedihydrate, polyphosphate, potassium dihydrogen phosphate, bisulfate, andsulfite, and, as well, the acetate, cyanurate, chloroacetate, formate,benzoate, fumarate, lactate, maleate, and phthalate, and mixturesthereof. These materials are characterized by poor or slight solubilityin pH 7 water at 20° C., and by slow conversion in the soil to a form inwhich the nitrogen is useful to plant life growing in the soil.

These nitrogen source materials, as ordinarily available commercially oras prepared, are in the form of very fine particles. In the case ofmelamine, for example, the commercially available product typically hascrystalline particles that are smaller in size than 10 mesh, U.S.Standard Sieve size, and generally, mostly smaller than 40 mesh. Thesevery fine, powdery nitrogen source materials are agglomerated throughthe use of a binder. Generally the binder forms at least 1% by weight ofthe powdery particles, preferably at least 2% by weight of the powderyparticles, and more preferably, at least 5% by weight of the powderyparticles. The binder may be selected from a broad spectrum ofmaterials, but preferably is selected to be compatible with the soil sothat it and any residue thereof is either inert, biodegradable,soil-conditioning, or has some plant nutrient value.

The binder that is used should be sufficiently strong, upon hardening orcuring, to impart to the granular agglomerates a crush strength of atleast one pound, as determined by tests on ten agglomerates randomlyselected, with sizes in the range from 3 mm. to 4 mm., the results beingaveraged. Preferably, however, the crush strength is at least 1.5pounds, and more preferably, 2 pounds or higher. A crush strength ofabout 1 pound is comparable to conventional, commercial prilled urea andis adequate strength for use in most forms of commercial application,including broadcast devices, spreaders, planter shank applicators, andfor dispensing from airplanes and helicopters.

Among the preferred binders are those selected from the group consistingof lignin sulfonate and its salts, starch, urea, urea-formaldehyderesins, melamine formaldehyde resins, and latices of synthetic polymericmaterials. Those binders are most preferred that have plant nutrientvalue, as do urea, urea-formaldehyde and melamine-formaldehyde resins.If such binders are essentially water-insoluble, they form granules thatcan be applied in the form of an aqueous slurry, if desired, as well asbroadcast by a spreader, airplane, or other conventional mechanism.

In another agglomeration technique, the melamine powder is combined witha suitable amount of a readily soluble binder material, i.e., forexample, with from 5% to 25% by weight of powdered urea to form a blend.This blend is then sprayed with water or with a solution of urea, in anagglomerating device such as on a rotating disc or in a rotating drum.In the case of a binder solution, the particles are coated. In the caseof a water spray, the urea either goes into solution or becomesmoistened and tacky, and in either state, coats the powdery melamineparticles sufficiently to cause agglomeration to occur. The agglomeratesare dried and cooled, to form hard composites having sizes primarily inthe range from about 1 mm. to about 10 mm., and preferably 3 mm. to 5mm. These composites have good crush strength and are substantially freefrom dusting.

Any of the conventional agglomerating techniques can be used to makeuseful granules. Thus, all of the binder can be applied in solution.When the binder is a material such as lignin sulfonate,urea-formaldehyde resin, or melamine-formaldehyde resin, application inthe form of a solution is usually most convenient. The binder might alsobe a material such as a phenolic resin, applied from a solution, butsuch a material, while having excellent characteristics as a binder, hasno nutrient value to contribute and is therefore less desirable. Thesame considerations apply generally to synthetic polymer latices.

The fertilizer granules may also be made in the form of prills. In theprilling operation, melamine powder is added to a molten bindermaterial, preferably urea, to form a slurry of the melamine powderparticles in the molten urea. Droplets of this molten slurry aresolidified by dropping them through a prilling tower, in theconventional fashion. While urea is the preferred material for use inpreparing prills, because of its nitrogen content and ready solubilityin water, and also because melamine is somewhat soluble in molten urea,other material such as sulphur could also be used, and mixtures ofmaterials could be used. In forming urea-bound prills, the prill productshould contain at least 33% by weight of urea, for adequate strength.When less urea is present, it is difficult to prepare a flowable slurry.The urea content of the prill may be as high as 90%, so that themelamine content may be in the range from 10% to 67% by weight of theprills. Preferably, the urea content is from 35% to 60% by weight of theprills, and more preferably, from 40% to 50% by weight. In terms ofnitrogen availability from a prilled urea-melamine product, the ureagenerally will contribute from about 25% to about 50% or more of thetotal nitrogen, but preferably contributes about 30% to 50%.

While preferred granular products are produced by agglomeration andprilling, satisfactory products can be produced by other techniques,including extruding techniques, pressing and granulating, andbricquetting. For example, melamine powder, or a powdered melamine salt,or the like, can be combined with a urea formaldehyde resin in powderform to form a mixture. The mixture can be pressed at an elevatedtemperature to cure the resin, and the resulting product can begranulated to form particles of the desired size, or the pressed, curedmass can be converted to flake form. Screening and recycling can be usedas necessary to develop granules of the desired sizes.

Readily soluble binders such as urea and salts such as ammonium nitratepermit rapid disintegration of the binder of the fertilizer granules inthe soil, with release of the fine melamine crystals or other materialfrom the group named above. This may be desirable where the compositecontains not only melamine but also a readily soluble, fast releasenitrogen fertilizer material. Where slow release is desired, thenordinarily one of the binders is employed that loses binding power moreslowly in the soil, such as, for example, a urea-formaldehyde resin or amelamine-formaldehyde resin.

Urea is a preferred binder for agglomerates, or for making prills,because it not only permits the production of fertilizer granules ofsufficient size, strength and weight for convenient application, but inaddition, the urea is readily soluble and adds valuable fast releasenutrient material to the soil. When used with a powdered nitrogen sourcecharacterized by poor or slightly solubility and slow conversion in thesoil to a useful form, the urea dissolves rapidly and releases the fineparticles of the poorly soluble nitrogen source into the soil, subjectto the action of water and of microorganisms, for slow dissolution orbiodegradation.

When an agglomerate is prepared from powdered melamine and a readilywater soluble binder such as urea, preferred proportions in the driedgranular product obtained are from 60% to 85% by weight of melamine andfrom 40% to 15% by weight of urea, or more preferably, from 67% to 80%by weight of melamine and from 33% to 20% by weight of urea.

When an agglomerate is produced using an insoluble or only slightlysoluble binder such as starch, a derivatized starch, or a modifiedstarch, lignin sulfonate, urea-formaldehyde, or melamine-formaldehyde,or one of the non-nutrient materials such as a phenolic resin, or asynthetic polymer in the form of a latex, a very slow release ofnitrogen from the melamine particles (or particles of other poorlysoluble nitrogen source) is obtained.

When a granular fertilizer product is used having a readilywater-soluble, fast release nitrogen fertilizer material as a binder, orwhen fine particles of a poorly water-soluble nitrogen source from thegroup above named is used in conjunction with a readily water-soluble,fast release nitrogen material, good results can be obtained atcomparatively low total nitrogen application rates, as will be describedpresently. The readily water-soluble, fast release material may beseparately applied, but preferably is applied simultaneously with thepoorly soluble nitrogen source. Thus the readily soluble fast releasematerial may be in solution in an aqueous medium in which the melamineor other particles are slurried or suspended. For the production of anagglomerate permitting a single application per growing season, fastrelease nitrogen fertilizer materials, generally an ammonium salt orurea, are advantageously used as the binder of the agglomerate. Examplesof such salt-type binder materials are ammonium sulfate, potassiumsulfate, ammonium phosphate, diammonium phosphate, the potassiumphosphates, ammonium nitrate, potassium nitrate, potassium chloride, andammonium chloride. When used as a binder material in the formation of anagglomerated composite, the proportion of such salt-type binder materialmay be from 15% to 40% by weight of the agglomerate, and preferably isfrom 20% to 33% by weight of the agglomerate. In terms of nitrogenavailability, the fast release salt generally will be present in anagglomerated product, such as an agglomerate of melamine particles, inan amount such that it provides from about 5% to about 30% by weight oftotal nitrogen, and preferably, from about 7.5% to about 25% totalnitrogen.

In addition, other materials may be incorporated in a granularfertilizer product. Such materials may provide micronutrients such aszinc, magnesium, iron and boron.

One of the advantages of the use of fertilizer compositions, applied inaccordance with the present invention, is that the rate of applicationmay be much lower in terms of nitrogen applied per acre than is truewith standard fertilizer practice. Because less of the active nitrogensources material is actually needed, it may be desirable, to facilitateapplication, in some cases, to incorporate an inert filler. Any of theconventional filler materials may be employed, such as, for example,gypsum, clay, sand, ground sea shells, ground dolomite, and groundlimestone.

Another important advantage of the use of fertilizer products applied inaccordance with the present invention is that, because of the slowrelease characteristics, it is possible to employ only a singleapplication per growing season. In addition, after the initialapplication, in the case of malamine-based fertilizer products inparticular, the release of nitrogen values into the soil appears tocontinue over two growing seasons. Consequently, in the second andsubsequent growing seasons, even lower rates of application may beemployed for given results, than may be used for the initialapplication.

Another aspect of the invention is the unexpected and surprising findingthat furnishing a majority or all of the nitrogen fertilizerrequirements by a nitrogen fertilizer source in accordance with thepresent invention apparently leads to a more effective production ofagricultural productive units per unit weight of nitrogen applied, andper unit of growing area. An agricultural productive unit is a seed,fruit, flower, vegetable, vegetable fiber, tuber, or the like. Inaddition, the practice of the invention apparently leads to overallyields of plant units comparable to those obtained when followingconventional, standard fertilizer practice, with its requirement for theuse of much higher nitrogen fertilizer application levels.

Based on the published literature, it would be expected that the use ofmelamine, or other s-triazine, or of an s-triazine salt, as a nitrogenfertilizer source, would be found to be less effective than urea orother standard readily soluble, fast release source of fertilizernitrogen. The results observed where nitrogen is furnished in accordancewith the present invention indicate that it often may be as much as twoor more times as effective as nitrogen from standard, fast release,readily water-soluble commercial fertilizers. It can be theorized thatthe fertilizer nitrogen sources of the present invention function insome novel way previously unknown and unrecognized.

Unexpectedly superior results are apparently obtained through theapplication of fertilizer in accordance with the present invention, inwhich the soil is furnished with a combination of poorly solublenitrogen material selected from the group of materials described above,and a conventional, readily water-soluble, fast release nitrogenfertilizer material. These superior results are manifested in two ways.First, an increased number of productive units is produced per unitarea. For wheat and rice, increased tillering appears to occur. Withgrapes, an increased number of clusters per vine apparently is produced.For potatoes, an increased number of tubers seems to appear per unitlength of row. Second, the total overall weight of these productiveunits for a given area apparently is increased. All of this is achievedat a reduced rate of application of nitrogen per acre as compared tostandard fertilizer practice, and generally with only a singleapplication of nitrogen fertilizer needed per growing season.

While not wishing to be burdened by theory, it is believed that whenmelamine is used, it is slowly sequentially degraded in the soil toammeline, ammelide and cyanuric acid and ultimately to urea andnitrates. Each of the three s-triazine hydrolysis products of melamine,and the s-triazine salts, undergo similar degradation. However, it isnot certain if any one, or some combination, of these s-triazines ortheir salts may be responsible for the unusual effects observed, infield evaluations.

In broad terms, this invention may be considered, in one aspect, as aprocess for increasing the effectiveness of standard readily soluble,fast release nitrogenous fertilizers in generating productive units inagricultural crops by supplementing their action with the use of a slowrelease, poorly or slightly soluble fertilizer nitrogen source. Thus, acombination of from about 10% to about 50% of the nitrogen in a standardreadily water-soluble, fast release nitrogenous fertilizer may becombined advantageously with from about 50% to 90% of a fertilizernitrogen source selected from the group of poorly and slightly solublematerials recited above.

The agricultural crops expected to respond with increased productiveunits to treatment in accordance with the invention includesubstantially all crops, but particularly those where fruit is theharvested unit rather than the entire plant. Such crops include foodgrains, feed grains, legumes, fibers, root crops, citrus, tubers,oil-bearing units including nuts, fruits and seeds, commercialvegetables, commercial melons, tree fruits, vine fruits, bush fruits andflowers. Exemplary food grains include wheat, rye, and rice. Feed graincrops include field corn, oats, barley and sorghum. Legumes includesoybeans, peanuts, beans and peas. Fiber crops include cotton, hemp andjute. Root crops include sweet potatoes and sugar beets. Citrus cropsinclude oranges, tangerines, grapefruit, lemons and limes. Tuber cropsinclude potatoes. Oil crops include flax, safflower, sunflower, andcastor bean. Commercial vegetable crops include lima beans, snap beans,beets, carrots, sweet corn, cucumbers, onions, green peas, and tomatoes.Commercial melon crops include cantaloupes, honeydews and watermelon.Tree fruit crops include apples, peaches, pears, cherries, and plums.Vine fruits include grapes. Bush fruits include the many different kindsof berries, especially raspberries and blueberries. Tree nut cropsinclude almonds, filberts, pecans and walnuts. These are intended to beexemplary only.

The invention will be better understood by reference to the followingexamples. Throughout this application and in these examples, allreferences to parts and percentages are by weight, and all references totemperatures are in degrees Celsius, unless expressly stated otherwise.

EXAMPLES OF THE FORMATION OF GRANULES THAT ARE USEFUL IN THE PROCESS OFTHE INVENTION

In all of the following examples, the melamine used was the commerciallyavailable product of Melamine Chemicals, Inc., Donaldsonville, La. Itwas a fine white crystalline powder having a screen analysissubstantially as reported above for commercially available melamine. Itwas about 99.9% pure, with specifications of a maximum moisture contentof 0.1%, maximum ash of 0.01%, and a density of about 1.57 g/ml.

As is pointed out in some of the following examples, crush strengths of1 lb. or greater are preferred. More preferably crush strengths of 3lbs. or more are developed, to facilitate application. Also, the bulkdensity of the granules should be 40 lbs./ft.³ or more. The preferredcombination of bulk density, crush strength, and particle size makes forflexibility in and ease of application.

EXAMPLE 1 Melamine Agglomerates Using a Urea Binder

Three batches of composite granules were made up, each containingdifferent amounts of urea and melamine, with urea serving as the binder.These batches of agglomerated granules were made in a pan agglomeratorof 9" diameter. The urea was first ground, and then blended with themelamine powder to form a homogeneous mixture. The powder mixture wasfed to the pan agglomerator and sprayed with a nearly saturated solutionof urea and water. The solution added about 7% urea to the driedagglomerate. The remainder of the urea content was derived from the ureapowder in the urea-melamine powder mixture.

Crush strengths of the three batches of granules after drying are shownin Table II, along with that of a comparison sample of commercial ureaprills. Crush strength was determined by randomly selecting ten granulesof 3 to 4 mm. in diameter from each batch, and subjecting each of theseten granules to pressure until crushing occurred. The ten values wereaveraged, and the average value is that reported in Table II below.

                  TABLE II                                                        ______________________________________                                                 Urea-Melamine Granule Crush                                                   Strength (Avg.)                                                               Batch Batch     Batch   Comparison-                                           No. 1 No. 2     No. 3   Urea Prills                                  ______________________________________                                        % Urea per 12      17        27     100**                                     batch, total                                                                  % Melamine 88      83        73     0                                         Crush Strength                                                                           1.9     2.9       3.0   1.1                                        (lbs.)                                                                        % total N  8.6     12.4      20.3  100                                        contributed                                                                   by Urea                                                                       ______________________________________                                         **Commercially available urea prills.                                    

EXAMPLE 2 Melamine Agglomerated with Urea Powder; Water Spray

One batch of agglomerated granules was prepared in a pan agglomerator asin Example 1, except that all of the urea was added as a powder, and thespray applied at the pan consisted only of water. The resultingcomposites contained 80% melamine and 20% urea, and after screening to3-4 mm., were found to have a crush strength of 2.1 lbs., using the sametesting technique as in Example 1.

EXAMPLE 3 Use of Other Binders for Agglomerating Melamine

Granular agglomerates were prepared with a 16" pan agglomerator usingmelamine with several different binders. In each case, the binder, inliquid form, was sprayed on the melamine. After drying, crush strengthwas determined as in Example 1. The results are reported in Table III,below.

                  TABLE III                                                       ______________________________________                                        Crush Strength Observed                                                       Melamine Agglomerated with Different Binders                                                      Crush Strength, lbs.,                                                         of 3-4 mm.                                                Binder              Agglomerates                                              ______________________________________                                        Calcium lignin sulfonate.sup.1                                                                    2.0                                                       UCAR 368 latex.sup.1                                                                              1.5                                                       Melamine-formaldehyde resin.sup.1                                                                 3.4                                                       Urea-formaldehyde resin.sup.1                                                                     1.0                                                       Diammonium phosphate (DAP).sup.2                                                                  0.2                                                       Ammonium nitrate.sup.2                                                                             0.33                                                     ______________________________________                                         .sup.1 Applied at 30%-50% solids. The dried agglomerates were about 5%        binder.                                                                       .sup.2 Substantially saturated solutions used. The dried agglomerates wer     approximately 93% melamine, 7% salt.                                     

EXAMPLE 4 Melamine Agglomerates With a Filler

Agglomerated granules were prepared by mixing a filler (waste filteraid) with melamine in equal proportions, then spraying the mixture in a16" pan agglomerator with a lignin sulfonate solution at 30% solids.After drying and screening, the resulting 3-4 mm. granules had a crushstrength of 0.75 lbs., determined as in Example 1.

EXAMPLE 5 Melamine Agglomerates

A mixture of melamine was granulated using a 40% solidsurea-formaldehyde spray. The dried screened products have a crushstrength of 1.0 lbs. in the 3-4 mm. diameter size range. Binder contentwas approximately 5% by weight.

EXAMPLE 6 Melamine Agglomerated with other Fertilizer Materials

Melamine, ammonium phosphate, and potassium chloride were blendedtogether in a 70:15:15 weight ratio. The mixture was fed to a 16" panagglomerator and sprayed with a 30% solids lignin sulfonate solution.The dried, screened granules had a crush strength of 2.2 lbs. in the 3-4mm. size range, and a binder content of 3%.

EXAMPLE 7 Melamine in Matrix of Solidified Urea Binder

Melamine and urea powder were blended in a 63-37 ratio. The blend washeated until a molten slurry was obtained. The slurry was then pouredonto a cooling slab so as to form both a thin film and a thick film.After cooling the thin film was broken into flakes.

The thick film, of about 4 mm. thickness, was broken into granules. Thecrush strength of the 3-4 mm. granules was exceptionally high, at 5.5lbs.

EXAMPLE 8 A Pressed Melamine-Urea Composite

A melamine-urea blend was formed as in Example 7. This blend was thenplaced in a heated platen press at about 500 psi for 5 minutes at 280°F. The resulting hot composite, in the form of a sheet about 4 mm.thick, was then removed from the press and allowed to cool. The cooledsheet was granulated, and 3-4 mm. granules of the composite had a crushstrength of 5.5 lbs.

EXAMPLE 9 Melamine-Urea 60/40 Prills

Melamine composite prills were prepared by heating 40 parts urea byweight with 60 parts melamine by weight. Heating was done in an aluminumcan using electric heating tape. A slurry formed at 275° F. Holes werethen punched in the can bottom, allowing the slurry to drip. A plasticsheet spread on the ground caught the falling prills as they droppedfrom the fourth story level.

The largest prills did not cool before landing and smashed. However, thesmaller prills cooled and solidified, and were collected for strengthtesting. Fairly good strength results were achieved, although notmeasured. Crush strength would be expected to be similar to the granulesof Example 7.

EXAMPLE 10 Melamine Agglomerated with a Latex Binder

5% Union Carbide UCAR 368 Latex, 15% water, and 80% melamine werecombined into a flowable slurry. A sheet of the slurry was formed andthen dried. An extremely strong composite resulted which could begranulated. The dried material contained 3% latex solids and 97%melamine. The crush strength of 3-4 mm. granules was 4.8 lbs.

EXAMPLE 11 Pressed Composite of Melamine and Urea-Formaldehyde

25 grams of urea, 70 grams melamine, and 15 ml. of 27% formaldehydesolution were mixed together and pressed at 300° F. and 500 psi to forma thick sheet. Crush strength of 3-4 mm. granules was 1.5 lbs.

EXAMPLE 12 Melamine-Urea Agglomerates for Field Trials

For field trials, 16,000 pounds of melamine/urea composites were madeusing 4 foot diameter pan agglomerators. Different composites wereproduced, at the melamine/urea ratios of 80/20, 75/25, and 67/33.Approximately 7% of the composites was provided by the urea added in theform of an aqueous binder solution, and the remaining urea was providedby powdered urea that was blended with the melamine powder prior toagglomeration.

General

In the foregoing examples, granular fertilizer products were preparedfrom commercially available, fine crystals of melamine. Similar granularfertilizer products can be prepared in substantially the same fashionfrom the hydrolysis products of melamine, i.e. ammeline, ammelide, ancyanuric acid, and from salts made from them and from melamine. Amongthe salts, the reaction product of nitric acid and melamine is apreferred material.

As with all fertilizer products, the granules should be made up for thespecific use intended, if possible. For example, an essentiallyinsoluble binder is preferred when the granular fertilizer product is tobe used for tree seedlings, or when the granules are to be applied in aslurry of water or of a water solution of a readily soluble, fastrelease nitrogen fertilizer such as, for example, UN-32. UN-32 is acommercially available product that is a combination of urea andammonium nitrate.

Where the granules are to be broadcast on the surface, soaked, thenturned under, generally either a soluble or insoluble binder, or acombination, may be used. The important result or objective to beattained is the distribution in the soil of essentially discrete fineparticles of the poorly or slightly soluble nitrogen source asspecified. Self-agglomerated crystals of melamine, for example, do notyield the effective, desired fertilizer action in the soil, presumablybecause the self-agglomerates make difficult or too slow the action inthe soil of water and/or microorganisms.

DEMONSTRATIONS OF USE OF THE INVENTION EXAMPLE 13 Field Trials withPotatoes

Field trials were conducted in Quincy loam soil. Standard fertilizerpractice on this particular land is expected, if followed, to producefrom about 25 to about 35 tons of potatoes per acre, with an averagefigure being about 30.

For comparison, an aqueous slurry was prepared of melamine and water, inan agitated supply tank. This was connected to a sprayer, and the slurrywas simply sprayed over the surface of the ground early in March, 1980.This produced an evenly distributed layer of fine particles of melamineon the surface of the ground.

The melamine was then mixed into the soil to a depth of about 6 inches.The soil was then turned over by plowing it to a depth of 14 inches.This distributed the melamine particles at depths in the range fromabout 6 inches to about 14 inches from the surface of the soil. Seedpotatoes were then planted on April 1.

From time to time, petiole nitrogen analyses and tuber counts weretaken.

For evaluation purposes, several different plots were treated in themanner described above. A control plot received no applied fertilizernitrogen. Other plots received different amounts of melamine, applied inthe manner described above. In addition, a plot was treated inaccordance with standard fertilizer practice (SFP). Generally there wasat least one replication plot prepared for each plot treated in themanner just described.

The petiole nitrogen analyses are reported in Table IV below.

                  TABLE IV                                                        ______________________________________                                        Petiole Nitrogen Analyses of Potatoes,                                        at Different Levels of Melamine Application                                   Melamine Application                                                                        Petiole Nitrogen, P.P.M. NO.sub.3                               lbs. N/acre   7/16    7/22      7/30  8/13                                    ______________________________________                                        0       (Control) 1100 to 1500                                                66                1700    1600     6000  7100                                 130               2500    2200    11200 10300                                 260               2600    4100    13000 13100                                 390               2600    2500    11200 11600                                 SFP*              16400   18800   20600 16500                                 ______________________________________                                         *Standard Fertilizer Practice, 600 pounds nitrogen per year, applied as       1620-0 material based on monoammonium phosphate, and the balance through      the application of UN32.                                                 

A comparison of the petiole nitrogen values reported in Table IVindicates that the melamine in the soil seemingly released nitrogen,that is useful to the potato plants, at a later time or slower rate thanoccurs when standard fertilizer practice is followed.

Some measurements were also made on the root, vine, and tuber weightsduring the growing season, as reported below in Table V.

                  TABLE V                                                         ______________________________________                                        Root, Vine, and Tuber Weights of Potatoes,                                    at Different Levels of Melamine Application                                                Root Wt. Vine Wt. Tuber Wt.                                      Melamine Application,                                                                      g.       g.       g.                                             lbs N/acre   8/5      8/5      8/5     10/8                                   ______________________________________                                        0      (Control) 187       853   4180    **                                   66               180       680   3220    **                                   130              200      1440   5380     8310                                260              220      1920   7900    12920                                390              180      1440   5820     9960                                SFP*             260      7700   7980    10960                                ______________________________________                                         *Standard Fertilizer Practice, 600 pounds nitrogen                            **Diedpreharvest due to verticullum wilt                                 

While the results reported in Table V above indicate very favorableresults at a melamine application rate of 260 pounds of nitrogen peracre, the results are not clear cut. Some of the potato plants involvedmay have been heavy-bearing mutants. Other potato plants involved mayhave been effected by the verticullum wilt.

However, for whatever the data may be worth, on August 5, the potatoesthat had been fertilized with melamine at the rate of 260 pounds ofnitrogen per acre produced vines whose weight was 1920 grams, whereaspotatoes fertilized in accordance with standard fertilizer practice inthe area produced vines having weights of 7700 grams. However, whencomparing the weights of the tubers produced, it would appear that thesmaller amount of melamine, in terms of applied nitrogen per acre, wassubstantially as effective as standard fertilizer practice.Supplementing the data in Table IV, the number of tubers noted on thatsame date in a linear five foot section of the plot treated withmelamine at the 260 pounds N per acre rate produced an average of 53tubers. In contrast, similar counts made on sections of five linear feetlength that had been treated in accordance with standard fertilizerpractice generated an average tuber count of 44 tubers. This wouldappear to be a substantial increase in tuber count, in favor of themelamine fertilizer applied at a much lower rate of applied nitrogen peracre than standard fertilizer practice.

Soil samples taken October 8 were tested, showing that at each level ofmelamine application, about 50% of the melamine remained in the soilafter the growing season.

In the second year, on the same areas, without the addition of furthernitrogen, the following petiole nitrogen results were obtained on newpotato plants.

                  TABLE VI                                                        ______________________________________                                        Second Year Petiole Nitrogen Analyses of Potatoes,                            at Different Levels of Melamine Application                                   Melamine Applied In                                                                        Petiole Nitrogen, PPM NO.sub.3                                   First Year, lbs N/acre                                                                     June     July    August                                          ______________________________________                                         0            9500     7000   potatoes died, early                                                          August                                           66          --       --      --                                              130          18000     4600    7000                                           260          13750    11000   10000                                           390          19600     7800    9800                                           SFP*         33000    18000   41000                                           ______________________________________                                         *Standard Fertilizer Practice, 650 pounds nitrogen added the second year.

Second year vine weight and tuber weight were also measured.

                  TABLE VII                                                       ______________________________________                                        Vine and Tuber Weights of Potatoes,                                           at Different Levels of Melamine Application                                   Melamine                                                                      Applied in Vine Wt.      Tuber Wt.                                            First Year,                                                                              g.            g.                                                   lbs N/acre Aug.   Sept.  Oct.  Aug.    Sept.                                  ______________________________________                                        0     Control  --     --                                                      66             died   early                                                                              --    --                                           130            1440   died --    5800(79)**                                                                            3840(49)**                           260            1380   died --    3960(34)                                                                              5980(43)                             390            1940   died --    5260(57)                                                                              4620(37)                             SFP*           4970   died --    5840(42)                                                                              8960(61)                             ______________________________________                                         *Standard Fertilizer Practice, 650 pounds nitrogen added again the second     year; but SFP would require crop rotation.                                    **The numbers in () are numbers of tubers per 5' of row.                 

These results show that nitrogen was available to the potatoes in thesecond year from melamine applied the previous year.

The quality of the potatoes fertilized with melamine is considered to beaverage as to smoothness and uniformity. The quality of the potatoesproduced following standard fertilizer practice is slightly lower.

The relatively poor yield (weights of tubers) from plants fertilizedwith melamine is believed to be attributable to the deaths of theassociated vines two to three weeks earlier than the death of the vinesfertilized according to Standard Fertilizer Practice. All of the vinesdied because of disease believed to be caused or brought on by failureto follow good crop rotation practice in this instance.

EXAMPLE 14 Potato Trials: Effect of Different Rates of Application

Melamine urea agglomerates were prepared using Ex. 1 techniques, at aratio of 67/33 melamine/urea. These agglomerates were applied as asource of fertilizer nitrogen to potatoes. For comparison, commercialurea/prills were also applied to comparison plantings. A controlplanting was treated with commercial urea-ammonium nitrate according tolocal Standard Fertilizer Practice.

The potatoes were the Russet Burbank variety. The observations made aresummarized in Table VIII below.

                                      TABLE VIII                                  __________________________________________________________________________    Potato Trials-Effect of Different Application Rates                           Applied                                                                            Melamine/                                                                Nitrogen                                                                           Urea  Petiole Nitrogen Analysis**                                                                     Weight (Sept.)                                                                          No. of                                 lbs./Acre                                                                          Ratio June                                                                              July                                                                              Aug. Sept.                                                                              Vine Tuber                                                                              Tubers***                              __________________________________________________________________________    143  67/33 12,000                                                                              8100                                                                            2000 6500 1040                                                                             g.                                                                              6560                                                                             g.                                                                              68                                     164   0/100                                                                              15,000                                                                            15,600                                                                            2500 1700 1640 8700 51                                     272  67/33 15,600                                                                              9700                                                                            2000 3100  960 9120 97                                     328   0.100                                                                              19,700                                                                            16,500                                                                            5000 9800 2390 8620 54                                     408  67/33 22,220                                                                            13,100                                                                            2000 4200 1800 9280 65                                     492   0/100                                                                              22,550                                                                            19,900                                                                            14,700                                                                             21,400                                                                             6320 6360 42                                     650  100*  11,900                                                                            16,600                                                                            14,100                                                                             28,400                                                                             3810 7440 43                                     __________________________________________________________________________     *Standard Fertilizer Practice. [urea/ammonium                                 **ppm nitrate.                                                                ***Number of tubers per plant measured in Sept.                          

On July 25, the melamine composite treated plants were compact, havingfew blooms. The urea treated plants had long vines and numerous blooms.The standard fertilizer practice treated plants had excessive vinegrowth, when compared to the agglomerated melamine/ureacomposite-treated plants.

EXAMPLE 15 More Potato Trials; Application for a Second Year

Melamine-urea agglomerates prepared as in Ex. 1 were applied to a oneacre plot that had been treated the previous year with a malemineslurry. In the earlier application, the slurry had been sprayed on thesurface of the soil, and then was first disced under, then ploughed in,to place the freshly applied discrete particles of melamine at a depthof 6" to 14", approximately. The agglomerates applied in the second yearwere broadcast on the soil surface by a spreader, then turned under, asbefore, to place them at a depth of 6"-14".

Standard fertilizer practice for potatoes in all second year trialsdescribed in these examples calls for the application of 650 lbs. N/acreper year. This is accomplished by the application of 600 lbs. of 16-20-0material based on monoammonium phosphate, and the balance through theapplication of UN-32. First year trials were made when SFP was to apply600 lbs. N/acre per year, primarily from monoammonium phosphate.

The observations made are reported in Table IX below.

                                      TABLE IX                                    __________________________________________________________________________    Potato Trials; Application for a Second Year                                                  Pounds of                                                     Second Year                                                                          Second Year                                                                            Melamine             Tuber Data                               Nitrogen                                                                             Nitrogen Source,                                                                       Nitrogen                                                                            Petiole Nitrogen Analysis,                                                                   Weight (Sept.,                           Applied                                                                              Melamine/Urea                                                                          Per Acre,                                                                           Second Year, ppm Nitrate                                                                     Second Year)                             lbs./Acre                                                                            Agglomerates                                                                           First Year                                                                          June                                                                              July                                                                              Aug.                                                                              Sept.                                                                            Tuber                                                                             No.                                  __________________________________________________________________________    130    67/33    130   11,000                                                                             4,100                                                                             2,200                                                                            died*                                                                            5,840                                                                             42                                   260    67/33    260   15,000                                                                             7,750                                                                            14,000                                                                            died*                                                                            4,700                                                                             47                                   390    67/33    390   21,000                                                                            12,200                                                                            12,200                                                                            died*                                                                            4,640                                                                             46                                    0     --        0     9,500                                                                            10,000                                                                             7,000                                                                            died*                                                                            2,460                                                                             35                                    650   --             23,800                                                                            41,000                                                                            20,900                                                                            died                                                                             8,960                                                                             61                                   Standard                                                                      Fertilizer                                                                    Practice                                                                      __________________________________________________________________________     Actually died 23 weeks earlier than plants on SFP.                       

The earlier deaths of the melamine-urea treated vines reported in TableIX is attributable to their enhanced susceptibility to disease becauseof planting potatoes in the same field two years in a row. The SFP fieldhad not had potatoes planted on it the previous year. Tuber quality frommelamine-urea agglomerate fertilized areas was average, while that fromareas subjected to standard fertilizer practice was less than average.

EXAMPLE 16 Grape Trials A. First Year

Gewurztraminer grapes were tested using melamine per se, in the firstyear, in a small vineyard. There were 540 2 year old Vinifera grapeplants per acre. The soil is a shallow sandy soil with a calichesub-base. General quality of the soil is poor, but it is well suited forVinifera grape production.

Complete rows of 66 plants were tested at each nitrogen level. Fulllength rows between the treated rows were used as controls. Replicateswere not deemed necessary because of the size of the plots, each rowbeing considered a plot. No nitrogen fertilizers had been used sincethese grapes were first planted. The vineyard owners felt thatconventional nitrogen fertilizer materials are too readily absorbed,stimulating vine growth rather than fruit production.

In March of the first year, furrows 5 inches deep by 10 inches wide weremade at a 12 inch distance from the center of the plants, along eachside of each row. A slurry of fine crystalline particles of melamine inwater was sprayed directly into each furrow, placing the melaminealongside of, and slightly above, the grape roots. The furrows were thenback filled with soil.

For these grape studies, the melamine applications were made at therates of about 60 lbs., 90 lbs., and 120 lbs. of N/acre. Ifconsideration is given to the slow rate of release, the application rateper season should be the annual application rate divided by a factor,probably of about 2.

Table X below reports on rates of application to the several test plots(rows).

                  TABLE X                                                         ______________________________________                                        Rates of Fertilizer Nitrogen Application                                      to Test Plots for Grapes                                                             Rates of Application in Lbs. N/Acre                                    Plot No. Melamine      (NH.sub.4)SO.sub.4                                                                      Total                                        ______________________________________                                        1        60.0          --        60.0                                         2        89.9          --        89.9                                         3        120.0         --        120.0                                        4        54.0           6.0      60.0                                         5        80.9           9.0      89.9                                         6        107.9         12.0      119.9                                        7        --            12.0      12.0                                         .sup. 8.sup.1                                                                          --            --        --                                           ______________________________________                                         .sup.1 Alternating rows served as controls; there were several.          

Lush vine growth, which tends to be produced by warm weather and readilyavailable nitrogen (nitrate) in the soil with sufficient soil moisture,is believed to interfere with the process by which the vines harden forwinter survival. Some vine varieties are more susceptible than others.These experiments with melamine, a very slow release nitrogen source,were therefore of potentially great signifigance for grape growers.Accordingly the vines were checked each week.

The entire vineyard outside of the test plot area received anapplication of standard practice fertilizer nitrogen, UN-32, at 50 lbs.N/acre, about the first of June. UN-32 is a commercial fertilizerconsisting of ammonium nitrate and urea. It was also applied to certainof the test plots, already treated, for a more careful comparison; seeTable XI, below. In the following few weeks, vine growth was moreabundant in the areas treated with UN-32, as compared to vine growth inthe test plots. The melamine-treated grapes had less cane growth andlesser degrees of green color, as compared to the UN-32 fertilizedvineyard area, but pollination and bunch size appeared about the same.

During late June and early July, the entire vineyard was irrigated everyseven days because of 90° F.-100° F. weather.

Grape yields at harvest, and bunch counts, are reported in Table XIbelow. Data from UN-32 treated areas of the vineyard, outside of thetest plot area, are included to provide a comparison with resultsobtained from standard fertilizer practice.

Grapes harvested from Plots 1-6 were compared as to pH. Differences weresmall. Grapes harvested from Plots 1-7 were compared as to sugar contentand acid content. The small differences observed appeared to be in favorof the use of the invention.

                                      TABLE XI                                    __________________________________________________________________________    Grape Yields and Bunch Counts                                                 Nitrogen Fertilizer Applied,                                                                     Yield of Grapes,                                                                         Bunch Count                                                                              Weight/                              lbs. N/Acre        lbs./plant,                                                                              per Plant, 100 grapes,                          Plot     Ammonium  Average of 8 plants                                                                      Average of 8 plants                                                                      in grams                             No.                                                                              Melamine                                                                            Sulfate                                                                             UN-32                                                                             Fertilized                                                                          Control.sup.1                                                                      Fertilized                                                                          Control.sup.1                                                                      Fertilized                                                                          Control.sup.1                  __________________________________________________________________________     1 60.0  --    --  17.6  13.8 117   108  142   149                             2 89.9  --    --  19.2.sup.2                                                                          16.7 .sup. 135.sup.2                                                                     127  144   130                             3 120.0 --    --  18.1.sup.3                                                                          18.1 .sup. 123.sup.3                                                                     131  144   148                             4 54.0  6.0   --  15.6  19.5 123   114  139   128                             5 80.9  9.0   --  11.5  16.0  83   121  145   134                             6 107.9 12.0  --  13.4  15.3 126   126  130   144                             7 --    12.0  --  12.4  16.0 104   120  134   --                              9 60.0  --    50  20.0  13.8 131   108                                       10 90.0  --    50  17.2  16.7 116   127                                       11 120.0 --    50  24.9  18.1 131   131                                       12 54.0  6.0   50  15.6  19.5 123   114                                       13 80.9  9.0   50  11.5  16.0  83   121                                       14 107.9 12.0  50  13.4  15.3 126   126                                       15 --    --    50  18.8.sup.4                                                                          13.8 .sup. 115.sup.5                                                                     108                                       16 --    --    50  24.6.sup.4                                                                          16.7 .sup. 156.sup.5                                                                     127                                       17 --    --    50  16.1.sup.4                                                                          18.1 .sup. 115.sup.5                                                                     131                                       18 --    --    50  21.8.sup.4                                                                          19.5 .sup. 130.sup.5                                                                     114                                       19 --    --    50  15.8.sup.4                                                                          16.0 .sup. 109.sup.5                                                                     121                                       20 --    --    50  18.3.sup.4                                                                          15.3 .sup. 118.sup.5                                                                     126                                       __________________________________________________________________________     .sup.1 The control plants were in rows immediately adjacent the fertilize     rows.                                                                         .sup.2 3% of the bunches were not mature and therefore were not saleable      (not included in reported weight).                                            .sup.3 4% of the bunches were not mature and therefore were not saleable      (not included in reported weight).                                            .sup.4 Average of all, i.e. plots 15-20: 19.2. Generally excessive vine       growth was observed in these plants. In addition, two samples measured 10     and 17% immature and unsaleable grapes (not included in reported weight).     .sup.5 Average of all, i.e. plots 15-20: 123.8.                          

B. Second Year

In the second year trials, the same plots and plants were used.Melamine-urea agglomerates, prepared as in Ex. 1, having an 80/20melamine/urea ratio, were shanked into the ground at a depth of about8", next to the roots. Bunch counts and yields were observed orestimated, respectively, in September, as reported below in Table XII.

                  TABLE XII                                                       ______________________________________                                        Grape Trials: Second Year of Application                                      Melamine                                                                      Application,       Melamine/                                                  lbs. Nitrogen/     urea                                                       acre year 1                                                                             Year 2   Ratio     Bunches/Plant Sept.                              ______________________________________                                        60        0        100/0     74                                               0         60       80/20     54                                               90        0        100/0     57                                               0         90       80/20     71                                               120       0        100/0     80                                               0         120      80/20     81                                               50        0        UN 32     68   (6 plant average)                           0         0        --        58   (2 plant average)                           ______________________________________                                    

EXAMPLE 17 Rice Trials

The present invention provides a technique to overcome the problem ofthe leaching out of fertilizer nitrogen sources in heavily waterburdened soils of the kind used for growing rice.

Two trials were run. Plot No. 1, consisting of 3.5 acres, had beentreated earlier in the year, according to local standard fertilizerpractice, with nitrogen at 18 lbs/acre and phosphorus at 48 lbs P₂ O₅per acre. For this trial, prills having a ratio of 75 parts melamine to25 parts urea binder were applied using a spinner spreader.

Plot No. 2, consisting of 3 acres, had not received any pre-seasonnitrogen application prior to the trials. It was treated with 75/25prills at the same rate as Plot No. 1.

Standard fertilizer practice during the growing season for the adjoiningplots, for comparison, was 100 lbs/acre of 18-48-0, and 130-140 lbs.N/acre as aqua ammonia, shanked into the soil to a depth of 4 inches,prior to planting.

The rice emerged above water about two weeks after planting. Anapplication of Bolero herbicide was made during the period between the14th day and 18th day after planting, at the rate of 40 lbs of 10 Gmaterial, for grass control.

Heads per square foot are reported in Table XIII below.

                                      TABLE XIII                                  __________________________________________________________________________    Rice Head Counts and Crop Yields                                              Lbs. N/Acre Applied           Rice                                                                              Head Count                                   Separate                     Height                                                                            Per 9 Sq. Ft.                               Plot No.                                                                           Applications                                                                           Total                                                                             Nitrogen Fertilizer Used                                                                  (in.)                                                                             8/8 9/9                                     __________________________________________________________________________    1    100          75/25 M/U prills                                                                          34  557 614                                                   118 18;48;0                                                           18                                                                           150          75/25 M/U prills                                                                          37  516 489                                                   168 18;48;0                                                           18                                                                           SFP*     153 see footnote*                                                                             40  497 397                                     2     50          75/25 M/U prills                                                                          30  222 306                                          100          75/25 M/U prills                                                                          30  242 237                                          150          75/25 M/U prills                                                                          30  236 266                                           0           --          --  --  217                                          SFP*         see footnote*                                                                             40  521 393                                     __________________________________________________________________________     *Standard Fertilizer Practice: 130-140 lbs. aqueous ammonia and 100 lbs       18:48:0 which combined equals 153 lbs N/acre.                            

When melamine/urea prilled composites are applied to rice, generallythere is a substantial increase in the extent of tillering, or puttingforth of sprouts from the base of the original heads. However, the ricetrials reported in this example did not live up to expectation. Plot 2was flooded from the side, and urea may have washed away prematurely, sothat tillering was reduced. In Plot 1, the rice head counts were huge.This plot was flooded from a corner, so less impact would be expected.

Generally, the rice grown under standard fertilizer practice conditionswas taller than the melamine-treated rice, and its straw looked heavier.

EXAMPLE 18 Corn Trials

Corn trials were conducted in sandy soil in a series of plots of a halfacre each within a 103 acre field. The melamine was shanked into thesoil as a slurry in water, at a depth of about 200 mm. (8 inches) belowthe surface. The following table shows the ear count per 100 plants atdifferent levels of application of melamine, and the ear weight per 100plants.

                  TABLE XIV                                                       ______________________________________                                        Ear Count and Ear Weight of Corn                                              at Different Levels of Melamine Application                                         Melamine Application                                                          Rate As Pounds   Ear Count/                                                                              Ear Wt/100                                   Plot #                                                                              N Per Acre       100 Plants                                                                              Plants, g.                                   ______________________________________                                        11     68              103       19110                                        22    141              111       24540                                        33    208              111       25520                                        55    Control*         100       19660                                        ______________________________________                                         *Ammonium sulfate applied at the rate of 43 lbs nitrogen/acre.           

The average number of ears per plant appears to have been increasedslightly by the use of melamine, shanked in. The average weight of theears also appears to have been increased somewhat, but the rate ofmelamine application was well above that of the control.

EXAMPLE 19 Corn Trials Using Melamine-Urea Agglomerates; Evaluation ofDifferent Application Techniques

Test plots totaling 40 acres of sandy to light loams and silts weretreated with different amounts of melamine agglomerates to provideseveral different levels of applied nitrogen per acre. Melamine-ureaagglomerated composites were used, prepared according to Example 1 andhaving 67 parts melamine to 33 parts urea binder; 75 parts melamine to25 parts urea binder; and 80 parts melamine to 20 parts urea binder. Thecomposites were successfully applied using different techniques: (1)spreading with a Barber spreader; (2) spreading with a Barber spreaderand plowing into the ground; (3) aerial application by airplane; (4)shanking into the ground during planting.

The results observed are summarized in Table XVA below.

                  TABLE XVA                                                       ______________________________________                                        Corn Trials-Effect of Application Method                                                                            Average                                 Nitrogen                     Number of                                                                              Number                                  Level   Melamine/  Application                                                                             Ears/100 of Ears                                 (lbs./acre)                                                                           Urea       Technique Plants   per Plant                               ______________________________________                                        140-150 75/25      (1)       155      1.55                                    140-150 75/25      (2)       147      1.47                                    140-150 75/25      (3)       155      1.55                                    150     80/20      (4)       153      1.53                                     0      (Control)  --        132      1.32                                    400     UN-32      **        129      1.29                                     400*   *                    145      1.45                                    ______________________________________                                         *Standard Fertilizer Practice, several applications during the growing        season.                                                                       **A total of 400 lbs. N in the form of UN32 applied in several                applications during the growing season to simulate Standard Fertilizer        Practice.                                                                

All of the test corn plantings reported in these examples, wherecompared, were made within one week of each other if not essentiallysimultaneous.

Corn grown in plots fertilized by method (2), broadcasting, then plowingin, looked green and robustly healthy. Corn grown in plots fertilized bybroadcasting only, methods (1) and (3), had yellow as well as greenfoliage, but was greener than corn fertilized by method (4), shanking inpost-planting, which looked yellow.

In an effort to approximate yields which would not be available untillater in the year, the ear counts in the same samples were retaken withthe following adjustments: full ears recorded as 1, small ears as 1/2,and nubbins as 0. This count has been recorded in Table XVB as effectiveear counts.

                                      TABLE XVB                                   __________________________________________________________________________    Corn Trials-Effect of Application Method                                                          Effective    Average Effective                            Nitrogen Level                                                                        Melamine/                                                                           Application                                                                         Number of                                                                           Number of                                                                            Number of Ears                               (lbs./acre)                                                                           Urea  Technique                                                                           Ears/100'**                                                                         Plants/100 ft.                                                                       per Plant                                    __________________________________________________________________________    140-150 75/25 (1)   109.5 109    1.0                                          140-150 75/25 (2)   118   126    0.94***                                      140-150 75/25 (3)   120.5 115    1.05                                         150     80/20 (4)   60    134    0.45                                          0      (Control)                                                                           --    40.5   95    0.43                                         400     UN-32 (1)   124.5 128    0.97                                          400*   *           145.5 159    0.92                                         __________________________________________________________________________     *Standard Fertilizer Practice, several applications during the growing        season.                                                                       **Full ears recorded as 1, small ears as 1/2, and nubbins as 0                ***Ear sizes were also of interest:                                           at 150 lbs. N, applied as a 75/25 melamine/urea prill: 51/2-6 cm. diam.       SFP: 41/2-5 cm. diam.                                                    

In a further evaluation, corn plants were harvested and weighed, an earcount was taken, and ear weights were recorded, from two test areas. Thefirst area was fertilized with 75/25 melamine/urea agglomerates bybroadcasting the agglomerates, then discing them in. The second area wasfertilized according to local standard fertilizer practice at 400 lbs.N/acre. Standard fertilizer practice calls for the application of atotal of 350 lbs. to 400 lbs. N per year per acre. This is accomplishedby three separate steps. First, an early application is made of 200 lbs.N/acre as anhydrous ammonia. Second, 400 lbs./acre of 16-20-0 is applied(based on monoammonium phosphate). Third, UN-32, comprises of urea andammonium nitrate, is applied through the irrigation sprinkler system.The results are summarized in Table VXI below. All samples taken werepre-dent.

                                      TABLE XVI                                   __________________________________________________________________________    Pre-dent Evaluation of Corn Response                                                                                      Ratio of Ear                                 Sample                                                                            Selection                                                                            Plants     Ears       Weight to                         Fertilization                                                                            No. Technique                                                                            Number                                                                             Weight                                                                              Number                                                                             Weight                                                                              Plant Weight                      __________________________________________________________________________    Melamine/urea 75/25                                                                      1   Random.sup.1                                                                         10   39 lbs.                                                                             20   18.5                                                                             lbs.                                                                             0.475                             Agglomerates, at                                                                         2   Random.sup.1                                                                         10   35.5  20   16    0.45                              150 lbs. N/acre.                                                                         3   all taken                                                                            58   122   59   47.5  0.39                              broadcast and  from a 50 ft.                                                  disced         row                                                            75/25 Agglomerates,                                                                      4   all taken                                                                            69   122   73   49.5  0.41                              at 235 lbs. N/acre,                                                                          from a 50 ft.                                                  broadcast and disced                                                                         row                                                            75/25 Agglomerates,                                                                      5   all taken                                                                            64   134   67   47.5  0.35                              at 150 lbs. N/acre,                                                                          from a 50 ft.                                                  flown on       row                                                            Standard Fertilizer                                                                      1   Random.sup.1                                                                         10   41    20   14    0.34                              Practice, 350 to 400                                                                     2   Random.sup.1                                                                         10   41    20   16.5  0.40                              lbs. N/acre                                                                              3   all taken                                                                            79   142   77   47    0.33                                             from a 50 ft.                                                                 row                                                            __________________________________________________________________________     .sup.1 In the random selection process, large plants have 2 ears each wer     taken from the ends of rows in open spots where there was a minimum of        competition from other corn plants.                                      

The data in Table XVI indicate that when the ratio of ear weight toplant weight is observed, the melamine/urea agglomerates have generatedmore weight of productive units per unit weight of foliage than did thestandard fertilizer practice.

EXAMPLE 20 Further Corn Trials, Using Melamine-Urea Agglomerates;Evaluation of Different Melamine:Urea Proportions

Agglomerates were prepared by using the techniques of Example 1, with abroad spectrum of different proportions of melamine to urea. In all ofthese trials, the fertilizer was applied by shanking it into the soilafter the corn had been planted and had sprouted sufficiently to definethe rows.

At approximately six months after planting, observations were made onthe number of ears/100 plants, the number of plants per 100 feet, andthe average number of ears per plant. The results are reported in TableXVII below. As in Ex. 13, effective ear counts were taken.

                                      TABLE XVII                                  __________________________________________________________________________    Corn Trials, Agglomerates at Different Melamine:Urea Proportions                                                     Average                                                                       Effective                              Applied                                                                            Melamine                                                                            Number of                                                                           Average Number                                                                         Effective    Number of                              lbs. Urea  Ears/ of Ears  Number Number of                                                                           Ears per                               N/Acre                                                                             Ratio*                                                                              100 Plants                                                                          per Plant                                                                              of Ears/100'                                                                         Plants/100'                                                                         Plant                                  __________________________________________________________________________    150  0/100 148   1.48     120.5  178   0.68                                        10/90 155   1.55     104.5  180   0.58                                        20/80 132   1.32     111.5  149   0.75                                        30/70 131   1.31     143.0  192   0.74                                        40/60 148   1.48     134.5  186   0.72                                        50/50  98   0.98     134.0  176   0.76                                        60/40 160   1.60     129.0  156   0.83                                        70/30 120   1.20     134.0  179   0.75                                        80/20 153   1.53     101.0  182   0.55                                        90/10 139   1.39     110.5  160   0.69                                        100/0 141   1.41      86.0  162   0.53                                    0   Control                                                                             132   1.32      81.0  190   0.43                                   400  UN-32 129   1.29     124.5  128   0.97                                    400,                                                                              Standard                                                                            145   1.45     145.5  159   0.92                                        Fertilizer                                                                    Practice                                                                 __________________________________________________________________________     *All melamine urea trials, shanked in after plant emergence.             

The data in Table XVII is interpreted as indicating that shanking in themelamine-containing agglomerates, or melamine per se, is not aneffective technique. The results also tend to indicate that pre-plantingapplication would be more effective.

EXAMPLE 21 Corn Trials: Effect of Different Rates of Application of75/25 Melamine:Urea Agglomerates

Agglomerates prepared by Ex. 1 techniques at 75/25 melamine:urea wereapplied at several different rates. The observations made are summarizedbelow in Table XVIII. The effective number of ears was also measured asin Ex. 13.

                  TABLE XVIII                                                     ______________________________________                                        Corn Trials; Effect of Different Application                                  Rates and Techniques                                                                                       Sept.   Sept.                                                                 Average Average                                  Applied                                                                              Melamine/             Number of                                                                             Effective                                lbs    Urea      Mode of     Ears/   Number of                                N/Acre Ratio     Application 100 Plants                                                                            Ears/Plant                               ______________________________________                                        107    75/25     Shanked pre-                                                                              1.85    0.45                                                      planting                                                     150    75/25     Broadcast & 1.47    0.94                                                      disc                                                         235    75/25     Broadcast & 1.59    0.92                                                      disc                                                         150     0/100    Shanked after                                                                             1.50    0.68                                                      planting                                                      0     Control   --          1.32    0.43                                     400,   UN-32     Broadcast and                                                                             1.45    0.92                                     Standard         applied in irri-                                             Fertilizer       gation water                                                 Practice                                                                      ______________________________________                                    

EXAMPLE 22 Wheat Trials

The effect of melamine applications at different levels was studied onthe wheat crop in soils generally classified as sandy to light loams andsilts.

Each trial was in one 2-acre plot. The several plots used were in alarge section of land having vary sandy soil to a depth of over fivefeet. This land had been planted to field corn in the previous year.Stalk residues were left on the surface, which was disced beforeplanting and after planting. The pre-planting discing was done after theapplication of the melamine slurry to the land.

While a simple melamine slurry was applied to the soil in three of thetest areas, in three others the liquid vehicle of the slurry was anammonium sulfate solution, and in a control plot, no fertilizer nitrogenwas applied. The rates of application are reported in Table XIX below.

                  TABLE XIX                                                       ______________________________________                                        Rates of Fertilizer Nitrogen Application                                      to Test Plots for Wheat                                                                Rate of Application in Lbs. N/Acre                                   Plot No.   Melamine    (NH.sub.4).sub.2 SO.sub.4                                                               Total                                        ______________________________________                                        1               66.6       --      66.6                                       2              133.2       --      133.2                                      3              200         --      200.                                       4               60         6.66    66.6                                       5              120         13.3    133.3                                      6              100         20      200                                        7              --          20      20                                         8     Control  --          --      --                                         ______________________________________                                    

The melamine was applied as a sprayed-on slurry in water using anOrchard Master 3 point sprayer having a 28-foot boom. The nozzlesoperate at 40 psi. Nugaines wheat at 96 pounds per acre was flown ontothe land by plane and disked into the soil two days later, about March17. Unfortunately, all plots received an application of urea solution byinadvertence, at a rate of about 100 pounds N/acre, through theirrigation sprinklers, on May 11.

This eliminated the control plot and nullified this wheat evaluationwork as to some of its objectives. However, three areas of evaluationwere still possible from these plots. First, the toxicity of melaminewhen used on wheat could be evaluated by making measurements of plantstand and yield. Secondly, the use of melamine as a supplementalnitrogen source to replace water-soluble nitrate nitrogen that may haveleached from the soil after long periods of irrigation can be evaluated.Soil samples were taken on March 11 and on May 27 to establish a baseamount of available nitrogen in the top 18 inches of soil. Periodicsubsequent sampling showed N movement in the soil. And third, it wasstill possible to evaluate whether melamine delivers nitrogen to thesoil for more than one growing season. If the nitrogen leaching weresignificant, the yields from the melamine plots should show increasedyields at harvest time.

The soil sample nitrate analyses are reported in Table XX below.

                  TABLE XX                                                        ______________________________________                                        Soil Sample Nitrogen Analyses                                                          Lbs. N/Acre Nitrate Nitrogen, PPM                                    Plot No.   Applied 3/17  3/11      5/27                                       ______________________________________                                        1              66.6 M.sup.1  5.8     5.82                                     2              133.2 M       4.3     6.32                                     3              200. M        1.5     11.95                                    4              60 M + 6.7 AS.sup.2                                                                         4.0     7.28                                     5              120 M + 13.3 AS                                                                             1.8     2.60                                     6              180 M + 20 AS 4.8     1.60                                     7              20 AS         --.sup.3                                                                              7.71                                     8     Control  --            7.4     3.96                                     ______________________________________                                         .sup.1 M = melamine                                                           .sup.2 AS = ammonium sulfate                                                  .sup.3 Specimen of soil lost, so no value is reported.                   

While the figures report erratic results, the trend seems to indicatethat the insertion of melamine alone in the soil produced a substantialincrease in available nitrate in the soil about 70 days after theinsertion.

The count on the heads of wheat is reported below in Table XXI.

                  TABLE XXI                                                       ______________________________________                                        Count of Heads of Wheat                                                                  Melamine     Heads of Increase                                                Application  Wheat    over                                         Plot No.   lbs N/acre   per ft.sup.2                                                                           Control                                      ______________________________________                                        1               66          52.6   57%                                        2              133          55.9   67%                                        3              200          55.0   65%                                        8     Control  none         33.4                                              ______________________________________                                    

The increase in heads of wheat from melamine nitrogen appears to showthat the melamine insertion was effective in increasing the productiveunits in wheat.

Conclusion

Pre-planting application of the melamine or the fertilizer material ispreferred, but not essential. The fine particles of melamine, or of itshydrolysis products, or of their salts, should be distributed in thesoil to permit the action of water and soil microorganisms on theparticles. The preferred mode of application is to broadcast theparticles, which may be in the form of granules, apply water through thesprinklers of an irrigation system, and then turn over the soil in sucha way as to effect a good distribution of essentially discretefertilizer particles in the soil, all before planting.

It appears to be important that the fertilizer particles be distributedthroughout the soil in such fashion that individual particles arepositioned to permit the action thereon of water and microorganisms.Slurry application as a film or thin layer in the bottom of a widetrench, that is later filled with soil, leads to good results. Shankingin seems to bunch the particles together rather than spread them apart,and the observed results tend to be disappointing.

When the particles are formed into granules, the binder should releasethe individual particles in the soil in such a way thatself-agglomeration of the particles is avoided. In other words, theparticles should be released from the granule in such a way that theyremain essentially discrete. Any application technique that tends toconcentrate particles together in the soil can be expected to lead toless than desired results, because the particles of melamine and othermembers of the group identified earlier may clump if moistened, and whenclumped, seem to resist dissolution by water and/or degradation bymicroorganisms.

The rate of application of the particulate slow release material, in thefirst year of its application, may be from 10% to 75% of the rate ofapplication for the entire growing season of a standard, readilysoluble, fast release nitrogen fertilizer material. A good fast releasematerial for such comparative purposes is a mixture of urea and ammoniumnitrate, such as UN-32. Preferably the rate of application according tothe invention is from 15% to 50% that of the standard, and morepreferably, from 20% to 40%. For the second and succeeding years, evenlower rates may be used, since there is some carryover from year toyear.

In the foregoing examples, the hydrolysis products of melamine and theirsalts, and the salts of melamine, may be used in place of melamine, withcomparable results.

While the invention has been disclosed in this patent application byreference to the details of preferred embodiments of the invention, itis to be understood that this disclosure is intended in an illustrativerather than in a limiting sense, as it is contemplated thatmodifications will readily occur to those skilled in the art, within thespirit of the invention and the scope of the appended claims.

What is claimed is:
 1. A process for increasing the output of productiveunits per unit weight of fertilizer nitrogen applied, from a crop thatresponds to fertilizer nitrogen, comprising inserting and distributingin soil in which said crop is grown, in the root zone of said crop,agranular fertilizer product that in the soil is a source of nitrogenfertilizer values, the granules being suitable for mechanical dispensingfor application to and into the soil, said granules consisting of amixture comprising: particles of a material selected from the groupconsisting of melamine, the mineral acid salts of melamine, and mixturesthereof, said particles having individual particle sizes not above 400micrometers in largest dimension, in an amount from 10% to 67% by weightof said granules, and an effective amount by weight of the granules, ofa binder that binds said particles in a form which is granular, theamount of said binder being from 33% to 90% by weight of said granules,said binder being urea, said binder, after distribution of the granulesin the soil, being capable of undergoing disintegration with release ofsaid particles thus permitting the action of water and microorganisms onsaid particles, said granules being suitable in granule strength andweight for mechanical dispensing and for application to or into thesoil, the average crush strength of a sample of said granules, selectedto have sizes of 3 mm. to 4 mm., being at least one pound per granule,and said granules having been formed by solidifying said urea binderfrom the molten state so as to bind said particles in said urea, andsaid particles furnishing from about 50% to about 90% of the fertilizernitrogen thus applied to the soil.
 2. The process of claim 1 whereinsaid crop is a food grain, a feed grain, a legume, a fiber crop, a rootcrop, a citrus crop, a tuber crop, a tree fruit, a tree nut, acommercial vegetable crop, a vine fruit, a bush fruit, a commercialmelon crop, or a crop.
 3. The process of claim 1 wherein said crop is afood grain crop.
 4. The process of claim 1 wherein said food grain isrice.
 5. The process of claim 1 wherein said crop is a feed grain crop.6. The process of claim 1 wherein said feed grain crop is field corn. 7.The process of claim 1 wherein said feed grain crop is barley.
 8. Theprocess of claim 1 wherein said crop is a tuber crop.
 9. The process ofclaim 8 wherein said tuber crop is potatoes.
 10. The process of claim 1wherein said particles are melamine particles, the binder material isurea, and wherein said binder has been solidified from the molten state.